The present invention relates to an induction sensor for sensing the displacement of a movable body by electromagnetic induction and, more particularly, to an induction sensor having a unique structure.
An induction sensor has customarily been used to sense the displacement of a movable body, e.g., a carriage included in a printer and movable in the right-and-left direction in a reciprocating motion. This kind of sensor has a scaler and a slider each being implemented by a substrate carrying a flat coil on one major stirface thereof. To sense a displacement by electromagnetic induction, the scaler and slider are positioned such that their surfaces carrying the coils thereon face each other. Specifically, the scaler, or sensor body, is affixed to the printer or similar apparatus while the slider is affixed to the carriage or similar movable body whose displacement should be sensed. As an AC current is caused to flow through the coil of the scaler, a displacement is determined in terms of the restilting voltage induced in the coil of the slider.
The prerequisite with the induction sensor is that the scaler and the slider be respectively mounted to the apparatus and the movable body at an accurate distance from each other (referred to as a gap length hereinafter) and at an accurate angle to each other (referred to as an azimuth angle hereinafter). However, it is extremely difficult and time consuming to mount the scaler and slider with such accuracy by hand.
In light of the above, Japanese Patent Laid-Open Publication No. 60-230881 discloses an induction sensor in which a scaler and a slider are movable relative to each other in order to change the gap length therebetween. With such an induction sensor, it is possible to adjust the gap length after mounting the scaler and slider to the apparatus and movable body and, therefore, to enhance the accuracy of the sensor. However, even this kind of scheme cannot allow the azimuth angle between the scaler and the slider to be adjusted.